The quality of a shaving instrument not only depends upon the exact position of the blade cutting edge relative to the face but also on the effectiveness of the guard bar to properly stretch and knead the skin and orient hair in correct position for optimum cutting by the blade edge.
One of the first patents to recognize this problem and suggest a solution is U.S. Pat. No. 2,048,565 to Rodrigues. In this patent, a safety razor is provided with a guard to impart a certain degree of friction upon the face of the user to cause the proper passage or what he calls "flow" of skin from the guard to the cutting edge of the blade. This razor guard presents the section of skin being shaved to the blade edge with the shaft of the hair extending out of the skin as far as possible when the edge of the blade sliding over the lather lubricated skin comes in contact with the hair. In effect, the action of the guard bar is likened to taking the portion of the skin immediately ahead of the blade edge between the fingers of the user and gently but firmly pressing it into a slightly convex form which naturally projects the shaft of the hair out of the cuticle as far as its roots will permit. The guard bar of this patent has a knurled or roughened area which contacts the skin to cause a slight accumulation of skin ahead of the bar.
A later development is disclosed in U.S. Pat. No. 2,349,252 to Douglass, wherein a wire guard is bent to a wavy or corrugated form which contacts the skin of the user prior to the razor blade.
Greek Patent No. 64526 to Gyllerstrom discloses a razor having a front bar which is mechanically or chemically treated to have pores, knurls, lines or other surface features to increase the friction upon the skin while shaving.
U.S. Pat. No. 4,502,217 to Schachter discloses a guard bar having a plurality of elements which are formed by coining, thereby displacing substantial amounts of material to achieve sharp edges extending parallel to the bar. These elements may be arranged symmetrically and are positioned on the surface portion of the guard bar which faces the blade in front of a tangential plane extending through the blade cutting edge and the surface of the guard bar. These teeth provide the necessary friction effects on the skin of the user.
In each of these prior art devices, the teeth or roughened area of the bar cannot be uniformly reproduced, since the tools used to form such teeth or roughened areas wear. This difficulty in preparing uniform roughening causes the guard bar to have unpredictable or ineffective areas which cannot achieve the desired results.
The present invention provides a novel method of manufacturing guard bars having a uniform texture for providing proper friction and drag on the skin of the user to facilitate optimal hair removal therefrom.